Gwynne-Jones was born in Richmond, Surrey. He was educated at Bedales
School and then qualified as a solicitor, but never practised. He
instead developed a love of art and began painting watercolours. In 1914
he began a course at the Slade School of Fine Art, but three months
later was commissioned into the Cheshire Regiment. He was wounded and
awarded the Distinguished Service Order (DSO) at the Battle of the Somme
in 1916. He returned to the Slade after demobilisation in 1919 and in
1923 became Professor of Painting at the Royal College of Art. He
remained at the Royal College for the remainder of his career, and also
gained renown for his own painting, most notably portraits and paintings
of flowers.